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Proceedings of The 39th International Conference on High Energy Physics — PoS(ICHEP2018)
The adapted DIRAC experiment at the CERN PS accelerator observed for the first time longlived hydrogen-like π + π − atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm and got broken up in the 2.1 µm thick platinum foil. Analysing the observed number of atomic pairs, n L A = 436 +157 −61 tot , the lifetime of the 2p state is found to be τ 2p = ( 0.45 +1.08 −0.30 tot ) · 10 −11 s, not contradicting the corresponding QED 2p state lifetime τ QED 2pdoi:10.22323/1.340.0453 fatcat:nq7idcw4djdxfe6iboba6j2564